code: def convert_postfix(postfix):
      if hasattr(postfix, "exp"):
          exp_nested = postfix.exp()
      else:
          exp_nested = postfix.exp_nofunc()
  
      exp = convert_exp(exp_nested)
      for op in postfix.postfix_op():
          if op.BANG():
              if isinstance(exp, list):
                  raise LaTeXParsingError(
                      "Cannot apply postfix to derivative"
                  )
              exp = sympy.factorial(exp, evaluate=False)
          elif op.eval_at():
              ev = op.eval_at()
              at_b = None
              at_a = None
              if ev.eval_at_sup():
                  at_b = do_subs(exp, ev.eval_at_sup())
              if ev.eval_at_sub():
                  at_a = do_subs(exp, ev.eval_at_sub())
              if at_b is not None and at_a is not None:
                  exp = sympy.Add(at_b, -1 * at_a, evaluate=False)
              elif at_b is not None:
                  exp = at_b
              elif at_a is not None:
                  exp = at_a
  
      return exp
  
imports: from importlib.metadata import version
  import sympy
  from sympy.external import import_module
  from sympy.printing.str import StrPrinter
  from sympy.physics.quantum.state import Bra, Ket
  from .errors import LaTeXParsingError
label_desc: Use image node_id 9 for calling a global function with example usage: convert_postfix(postfix) and returns: exp